Summary:This clip from Al Gore's An Inconvenient Truth uses visual displays of scientific data to demonstrate that global temperatures and levels of carbon dioxide are higher than ever before, showing that this urgent problem is caused by human activity (start film at 13:25; end at 23:07). He documents several impacts in the real world, including receding glaciers, noting that 40% of the people on Earth receive their drinking water from glaciers and that they will face a shortage in the future. A reasonable and skeptical viewer may note that ice ages are cyclical, which is correct. But using core drills of ice, scientists are able to measure carbon dioxide levels and surface temperatures going back 650,000 years. This allows the viewer to see cycles from the past 7 ice ages. The data shows that in those 650,000 years, carbon dioxide levels never went above 300 parts per million--until recently. By visualizing the data, we can see that the CO2 level today is far above the level that it has ever been in that time frame. Gore compares the CO2 levels and temperature levels (as shown in the graphic here) and argues this scientific fact: "when there is more carbon dioxide, the temperature gets warmer because it traps more heat from the sun inside." He then shows the projected level that CO2 is expected to rise to in 50 years. In short, CO2 levels are higher than ever before; when CO2 rises, temperatures rise. Therefore, the Earth's temperature will continue to rise. Because CO2 levels are outside of any natural cycle, it is human activity that has caused it, and the consequences will continue to worsen. There are also a variety of sites online that have additional data and evidence, which may be useful in discussing global climate change in the classroom (e.g. ClimateCrisis.net; EPA).Submitted By:Paul Dean